Re: Some basic modeling results

From: Nick Holford n.holford@auckland.ac.nz Subject: Re: [NMusers] Some basic modeling results Date: Fri, 06 Oct 2006 10:09:37 +1300 Susan, Evidence for the bias in FO can be found in the earliest publications describing NONMEM's performance with simulated data. I cannot at the moment produce a published reference which directly compares the two estimation methods. I expect someone else can do that. The second issue is trickier. I have been working on a simulation project for some years now with Diane Mould and Joga Gobburu that has tried to answer your question. We have still not reached a fully satisfactory conclusion but my own impression is that simply using the diagonal for OMEGA does not consistently bias the fixed effect parameters when off-diagonal elements are included in OMEGA for simulating the data. Nick -- Nick Holford, Dept Pharmacology & Clinical Pharmacology University of Auckland, 85 Park Rd, Private Bag 92019, Auckland, New Zealand email:n.holford@auckland.ac.nz tel:+64(9)373-7599x86730 fax:373-7556 http://www.health.auckland.ac.nz/pharmacology/staff/nholford/ _______________________________________________________